What did the ice edge look like when the Irish Sea Glacier came inland from the Bristol Channel? There are a number of options -- above are two examples from Greenland.
Let's imagine that this is the Irish Sea Glacier, pushing inland into Somerset from the NW. The one photo (from Google Earth) shows incredibly clean ice with virtually no morainic material and a scraped and eroded bedrock floor. This is from North Greenland -- here there is deep and continuous permafrost and virtually no bottom melting beneath the ice sheet. The glacier is probably frozen to its bed, and moves largely through internal deformation. There is probably not much erosion going on today.
The other photo is from South Greenland, showing ice that is rapidly on the way out. It is dirty and thin, and there is water everywhere. Here the glacier is clearly sliding and is wet-based, so there is probably much erosion up-glacier and a vast amount of deposition.
Of course, during a glaciation conditions can swing from one extreme to another, with cold and clean ice at the peak (ie coldest part) of the glacial episode, and melting, erosion and dumping of debris towards the end of the glaciation, as the climate warms and the ice edge goes into retreat.